FLAG expression is detected by FACS in both PB granulocytes and lymphocytes of rats receiving SV(Nef-FLAG). Blood from all rats that were injected as in Figure 4 legend was double-immunostained (after erythrocyte lysis) for FLAG and mature leukocyte lineage markers. FLAG and lineage marker expression among the several hematopoietic subpopulations was tested by flow cytometry beginning at 14 weeks after injection. Data were analyzed using Cell Quest software. (A) Time course of FLAG expression in PB granulocytes and CD3⁺ lymphocytes of rats injected with SV(Nef-FLAG). Background immunostaining for FLAG in control vector recipients was subtracted. (B) Representative FACS scattergrams for FLAG and lineage marker expression, shown here at 32 weeks after injection for PB granulocytes (top panels) and CD8⁺ T lymphocytes (bottom panels). Percentages shown are FLAG⁺ and lineage⁺ cells as a percentage of total lineage⁺ cells for that lineage.